Main beam-small beam joint structure

Abstract

To provide a girder-beam connection structure enabling high-strength bolt friction joint between a lower flange of a beam and a girder with sufficient joining strength.SOLUTION: A girder-beam connection structure 1 according to the invention comprises: a beam upper flange connection part 7 at which beam upper flanges 5a are rigidly connected to a girder upper flange 3a, or the beam upper flanges 5a are rigidly connected to each other; a beam web connection part 9 at which a beam web 5b is rigidly connected to a vertical plate 19 connected to a girder web 3b; and a beam lower flange connection part 11 at which beam lower flanges 5c are connected to a pair of lower flange side horizontal plates 23, respectively, that are connected to a girder lower flange 3c and disposed across the beam lower flange 5c in a width direction. The beam lower flange connection part 11 is formed by connecting the beam lower flange 5c and the lower flange side horizontal plate 23 with high-strength bolts 17 to two connection plates 25 disposed on upper faces and lower faces of the beam lower flange 5c and the lower flange side horizontal plate 23 so as to straddle them.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a connection structure between a main beam and a secondary beam of a framework in a steel frame structure.

Background Art

[0002] Conventionally, a framework for supporting a concrete floor in a steel frame structure is composed of main beams arranged in parallel at a predetermined interval and secondary beams arranged to connect the main beams. When a vertical load is applied to the central part of the secondary beam, the secondary beam deflects, and due to the rotational deformation (angle) occurring at the joint between the main beam and the secondary beam, cracking of the concrete occurs near the joint between the main beam and the secondary beam. Therefore, a technique for reducing the deflection of the secondary beam is required.

[0003] Therefore, Patent Document 1 discloses a technique in which two secondary beams arranged in a butted state on both sides of a main beam are connected to each other via a slab placed across the upper flange of the main beam and the upper flange of the secondary beam, and the two secondary beams are configured as a continuous beam. According to the technique of Patent Document 1, two secondary beams can be configured as a continuous beam without joining the upper flanges of the secondary beams to the upper flange of the main beam.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In Patent Document 1, as described above, the upper flanges of the secondary beams are connected without passing through the upper flange of the main beam. On the other hand, the lower flange of the secondary beam is joined to the connecting flange of a joint member fixed to both sides of the web of the main beam. The connecting flange, which is positioned at the same height as the lower flange of the joist, and the lower flange of the joist are positioned to abut each other. This abutted joint is sandwiched from above and below by two splice plates, and the splice plates and the lower flange of the joist, and the splice plates and the connecting flange are fastened together with multiple bolts.

[0006] In Patent Document 1, the lower flange of a joist and the connecting flange are joined by a high-strength bolt friction joint with two-sided shear, thereby joining the lower flanges of opposing joists to each other via the connecting flange. Since the stress acting on the lower flange of one joist is transmitted to the lower flange of the other joist via the connecting flange, the high-strength bolt friction joint must be constructed with sufficient strength to resist this transmitted stress.

[0007] To increase the joint strength of high-strength bolt friction joints, it is advisable to extend the length of the splice plate to increase the friction area, and to add more bolts on both the connecting flange side and the secondary beam side. However, in the configuration of Patent Document 1, the group of connecting bolts on the main beam side must be placed in a very narrow area, approximately half the width of the main beam flange multiplied by the width of the secondary beam flange. This makes it difficult to increase the number of bolts, and there is a risk that the joining force will be insufficient when large stresses are applied.

[0008] This invention was made to solve the above-mentioned problems, and aims to provide a beam-beam joint structure that allows the lower flange of a secondary beam to be frictionally joined to a main beam with high-strength bolts with sufficient joint strength. [Means for solving the problem]

[0009] (1) The main beam-secondary beam joint structure according to the present invention is a structure in which a main beam made of H-shaped steel is joined to a main beam made of H-shaped steel, with a pair of secondary beams made of H-shaped steel having the same beam depth as the main beam, on either side of the main beam in a direction perpendicular to the main beam, A joint section is formed by rigidly connecting the upper flanges of opposing beams to the upper flange of a main beam, or by rigidly connecting the upper flanges of opposing beams to each other via a member, The beam webs of opposing beams are rigidly connected to vertical plates attached to the main beam webs, forming a beam web joint. The lower flanges of opposing joists are joined to the lower flanges of the main beams, and each joists is joined to a pair of horizontal plates on the lower flange side that are positioned to sandwich the lower flanges of the joists in the width direction, and these plates form a joist lower flange joint. The lower flange joint of the beam is characterized in that the lower flange of the beam and the horizontal plate on the lower flange side are joined to two joining plates, which are positioned on the upper and lower surfaces of the beam and the horizontal plate on the lower flange side, respectively, by high-strength bolts.

[0010] (2) Furthermore, the main beam-secondary beam joint structure according to the present invention is a structure in which a main beam made of H-shaped steel is joined to a main beam, with a pair of secondary beams made of H-shaped steel having a smaller beam depth than the main beam, on either side of the main beam in a direction perpendicular to the main beam, A joint section is formed by rigidly connecting the upper flanges of opposing beams to the upper flange of a main beam, or by rigidly connecting the upper flanges of opposing beams to each other via a member, The beam webs of opposing beams are rigidly connected to vertical plates attached to the main beam webs, forming a beam web joint. The lower flanges of opposing joists are joined to the web of the main beam, and each joists is joined to a pair of horizontal plates on the lower flange side that are positioned to sandwich the lower flanges of the joists in the width direction, and the lower flanges of the joists are joined to these joists. The lower flange joint of the beam is characterized in that the lower flange of the beam and the horizontal plate on the lower flange side are joined to two joining plates, which are positioned on the upper and lower surfaces of the beam and the horizontal plate on the lower flange side, respectively, by high-strength bolts.

[0011] (3) In addition, in the case described in (1) or (2) above, the beam upper flange joint is formed by joining the beam upper flanges of opposing beams to a pair of upper flange-side horizontal plates that are joined to the beam upper flange and are arranged to sandwich the beam upper flanges in the width direction. The upper flange joint of the beam is characterized in that the upper flange of the beam and the horizontal plate on the upper flange side are joined to two joining plates, which are positioned on the upper and lower surfaces of the beam and the horizontal plate on the upper flange side, respectively, by high-strength bolts.

[0012] (4) Furthermore, the main beam-secondary beam joint structure according to the present invention is a structure in which a main beam made of H-shaped steel is joined to a main beam with a pair of secondary beams made of H-shaped steel facing each other on both sides of the main beam in a direction perpendicular to the main beam, The upper flanges of opposing joists are joined to the upper flange of the main beam, and each is joined to a pair of upper flange-side horizontal plates that are positioned to sandwich the upper flange of the joist in the width direction, forming a joist upper flange joint. The beam webs of opposing beams are rigidly connected to vertical plates attached to the main beam webs, forming a beam web joint. The lower flanges of opposing joists are rigidly connected to the main beam, or the lower flanges of opposing joists are rigidly connected to each other via a member, forming a joist lower flange joint. The aforementioned beam upper flange joint is characterized in that the beam upper flange and the upper flange side horizontal plate are joined to two joining plates, which are positioned on the upper and lower surfaces of the beam upper flange and the upper flange side horizontal plate, respectively, by high-strength bolts.

[0013] (5) In addition, in any of the above (1) to (4), the bonding plate has a specified lower limit of yield strength of 355 N / mm 2 The above is the characteristic feature. [Effects of the Invention]

[0014] In the present invention, since the lower flange of the cross beam is frictionally joined to a pair of lower flange side horizontal plates arranged with the cross beam sandwiched therebetween in the width direction, it becomes easy to increase the frictional area of the joint portion and to add bolts. Therefore, even when the stress acting on the cross beam is large, the joint strength required for stress transmission can be ensured.

Brief Description of the Drawings

[0015] [Figure 1] It is an explanatory view of the girder-cross beam joint structure according to the embodiment. [Figure 2] It is a cross-sectional view taken along the line A-A of FIG. 1. [Figure 3] It is an end view taken along the line B-B of FIG. 2. [Figure 4] It is an explanatory view of another aspect of the girder-cross beam joint structure according to the embodiment (Part 1). [Figure 5] It is a cross-sectional view taken along the line C-C of FIG. 4. [Figure 6] It is an end view taken along the line D-D of FIG. 5. [Figure 7] It is an explanatory view of another aspect of the girder-cross beam joint structure according to the embodiment (Part 2). [Figure 8] It is a cross-sectional view taken along the line E-E of FIG. 7. [Figure 9] It is an end view taken along the line F-F of FIG. 8. [Figure 10] It is an explanatory view of another aspect of the girder-cross beam joint structure according to the embodiment (Part 3). [Figure 11] It is an end view taken along the line G-G of FIG. 10. [Figure 12] It is an explanatory view of another aspect of the girder-cross beam joint structure according to the embodiment (Part 4).

Modes for Carrying Out the Invention

[0016] One embodiment of the present invention, a main beam-secondary beam joint structure 1, shows a joint structure between a main beam constituting the floor frame structure of a steel-framed building and a pair of secondary beams facing each other on either side of the main beam. An example where the secondary beam and main beam have the same beam depth is shown in Figures 1 to 3, and will be explained in detail below. Note that Figure 3 is an end view showing only the cross-sectional end face of the secondary beam, with the main beam omitted.

[0017] As shown in Figures 1 to 3, the main beam-secondary beam joint structure 1 is formed by joining a main beam 3 made of H-shaped steel to a pair of secondary beams 5 made of H-shaped steel, which are positioned opposite each other on both sides of the main beam 3 in a direction perpendicular to the main beam 3. The main beam-secondary beam joint structure 1 includes a secondary beam upper flange joint 7, which joins the upper flanges 5a of the pair of secondary beams 5 together; a secondary beam web joint 9, which joins the secondary beam web 5b to the main beam 3; and a secondary beam lower flange joint 11, which joins the secondary beam lower flange 5c to the main beam 3. The following provides a detailed explanation of each joint.

[0018] <Joint at the upper flange of the secondary beam> As shown in Figure 1, the secondary beams 5 (hereinafter simply referred to as "opposing secondary beams 5") that are opposite each other on either side of the main beam 3 are positioned at a height where the upper flange 5a of each secondary beam forms the same plane as the upper flange 3a of the main beam 3. Two vertical plates 13 are provided on the upper surface of the upper flange 5a of each opposing beam 5, and are joined in an upright position in the direction of the beam axis (see Figure 3). These vertical plates 13 should be welded to the beams 5 in advance at the factory.

[0019] On both sides of each vertical plate 13, two connecting plates 15 are arranged to straddle the opposing vertical plates 13 (the vertical plate 13 of one beam 5 and the vertical plate 13 of the other beam 5 opposite to it), and these are joined by high-strength bolts 17 (high-strength bolt friction joint).

[0020] As described above, the upper flanges 5a of opposing beams 5 are rigidly connected via the vertical plate 13 and the connecting plate 15. This allows stress acting on the upper flange 5a of one beam 5 to be transmitted to the upper flange 5a of the other beam 5. A rigid connection refers to a strong joint that does not produce rotational deformation (angle).

[0021] <Beam web joint> A pair of vertical plates 19 are provided on both sides of the main beam web 3b of the main beam 3, arranged to form a coplane with the secondary beam web 5b of the opposing secondary beam 5. The vertical plates 19 are plate-shaped members with the same shape as the area enclosed by the main beam upper flange 3a, main beam web 3b, and main beam lower flange 3c, and are positioned to cover this area and joined to the main beam upper flange 3a, main beam web 3b, and main beam lower flange 3c.

[0022] A splice plate 21 is positioned on both sides of the beam web 5b and the vertical plate 19, straddling both. The splice plate 21 is fastened to the beam web 5b, and the splice plate 21 is fastened to the vertical plate 19, respectively, by high-strength bolts 17. As described above, the beam webs 5b of opposing beams 5 are rigidly connected to the main beam web 3b via the vertical plate 19 and the splice plate 21, respectively.

[0023] <Joint at the lower flange of the joist> As shown in Figure 2, a pair of lower flange-side horizontal plates 23 (shown in dark gray) are joined to both sides of the lower flange 3c of the main beam 3, sandwiching the lower flange 5c of the secondary beam in the width direction. These lower flange-side horizontal plates 23 are preferably welded to the lower flange 3c of the main beam in advance at the factory.

[0024] The horizontal plate 23 on the lower flange side shall be made of the same thickness and strength material as the lower flange 5c of the secondary beam. The width of the horizontal plate 23 on the lower flange side may be at least half the width of the lower flange 5c of the secondary beam, but it is desirable that the width be sufficient to ensure adequate strength at the welded joint with the lower flange 3c of the main beam. Furthermore, to accommodate errors during construction, it is advisable to set a clearance of approximately 10 mm between the outer edge of the lower flange horizontal plate 23 and the lower flange 5c of the secondary beam.

[0025] The sides of the lower flange 5c of the joist are friction-jointed with high-strength bolts to the adjacent lower flange-side horizontal plate 23. Specifically, two joining plates 25 (shown in light gray) are positioned on the upper and lower surfaces, respectively, straddling the lower flange 5c of the joist and the lower flange-side horizontal plate 23, and the lower flange 5c of the joist and the lower flange-side horizontal plate 23 are joined to the joining plates 25 with high-strength bolts 17.

[0026] As a result, the stress (compressive force) acting on one of the lower flanges 5c of a secondary beam is transmitted to the other lower flange 5c of a secondary beam via the high-strength bolt 17, the connecting plate 25, the lower flange side horizontal plate 23, and the lower flange 3c of the main beam. To withstand this stress transmission, the diameter and arrangement (number) of the high-strength bolts 17, as well as the specifications of the connecting plate 25 (yield strength, plate thickness, length, etc.), are designed based on the cross-sectional area and yield strength of the lower flange 5c of the beam.

[0027] In the conventional example described above, the lower flange 5c of the beam and the horizontal plate 23 on the lower flange side were butted together in the longitudinal direction of the beam 5 and friction-jointed with high-strength bolts. As a result, there was a limit to the number of high-strength bolts 17 that could be placed, and there was a risk that a sufficient joint force to withstand stress transmission could not be achieved. In this respect, in this embodiment, the lower flange side horizontal plate 23 is positioned so as to sandwich the lower flange 5c of the joist in the width direction, making it easy to add high-strength bolts 17.

[0028] For example, the lower flange side horizontal plate 23 and the connecting plate 25 may be extended in the direction of the beam axis to increase the number of high-strength bolts 17 and improve the joining strength. Also, if the width of the lower flange 5c of the beam is large, the lower flange side horizontal plate 23 and the connecting plate 25 may be enlarged in the direction of the beam width, and two or more rows of high-strength bolts 17 may be placed on both the beam side and the lower flange side horizontal plate 23 side.

[0029] Furthermore, since the stress acting on one lower flange 5c of a secondary beam is transmitted to the other lower flange 5c of a secondary beam via the lower flange 3c of the main beam, if the yield strength of the lower flange 3c of the main beam is lower than the yield strength of the lower flange 5c of a secondary beam, it is possible that the lower flange 3c of the main beam will not be able to withstand the transmitted stress. In this respect, this embodiment can distribute the stress transmitted to the lower flange 3c of the main beam by increasing the width of the lower flange side horizontal plate 23, thereby reducing the risk of damage to the lower flange 3c of the main beam. When the width of the lower flange side horizontal plate 23 is increased, the welded portion with the lower flange 3c of the main beam becomes larger, so stress is transmitted to a wider area of ​​the lower flange 3c of the main beam. Therefore, the stress acting on the lower flange 3c of the main beam is distributed, making it less likely for the lower flange 3c of the main beam to be damaged. As described above, even when the yield strength of the lower flange 3c of the main beam is lower than the yield strength of the lower flange 5c of the secondary beam, the risk of failure of the lower flange 3c can be reduced by increasing the width of the horizontal plate 23 on the lower flange side.

[0030] The steel used for the joining plate 25 has a specified lower limit of yield strength of, for example, 355 N / mm². 2 It is desirable to use the above-mentioned high-strength material. By constructing the joining plate 25 from a high-strength material, it becomes possible to reduce the thickness of the joining plate 25, which can be expected to result in a more compact joint and improved workability.

[0031] As described above, in this embodiment, the lower flange side horizontal plate 23 is positioned to sandwich the lower flange 5c of the beam in the width direction, and the lower flange 5c of the beam is friction-joined to the lower flange side horizontal plate 23 with high-strength bolts. This allows for an increase in the friction area and the addition of more bolts, enabling resistance to greater stresses than in the conventional method.

[0032] The above explanation shows an example where the beam depth of the main beam 3 and the secondary beam 5 are the same. However, when the beam depth of the secondary beam 5 is smaller than that of the main beam 3, the configuration is as shown in Figures 4 to 6. The upper flange joint 7 and the web joint 9 of the secondary beam in the main beam-secondary beam joint structure 27 shown in Figures 4 to 6 are the same as in the example in Figures 1 to 3, so the same reference numerals are used and their explanation is omitted. Only the lower flange joint 11 of the secondary beam will be explained below.

[0033] In this example, the lower flange side horizontal plate 23 is formed in an L-shape, as shown in Figure 5. This L-shaped lower flange side horizontal plate 23 is positioned at the same height as the lower flange 5c of the secondary beam and is joined in pairs to both sides of the main beam web 3b. The pair of lower flange side horizontal plates 23 are positioned facing each other with their L-shapes reversed, and the lower flange 5c of the secondary beam is positioned in the space between them. The portions of the pair of lower flange-side horizontal plates 23 that protrude from the main beam 3 sandwich the lower flange 5c of the secondary beam in the width direction, and these portions and both sides of the lower flange 5c of the secondary beam are friction-jointed with high-strength bolts. Specifically, the lower flange 5c of the secondary beam and the lower flange-side horizontal plates 23 are joined to two connecting plates 25, which are positioned on the upper and lower surfaces respectively, straddling the aforementioned portions of the lower flange-side horizontal plates 23 and the lower flange 5c of the secondary beam, with high-strength bolts 17.

[0034] The shape of the lower flange-side horizontal plate 23 can be rectangular in a top view, as shown in the example in Figure 2, but by making it L-shaped as in this example, the lower flange-side horizontal plate 23 can also be joined to the vertical plate 19. This reinforces the lower flange-side horizontal plate 23 and distributes the stress acting on the main beam 3. In addition, in this example, reinforcing stiffeners 29 are provided on both sides of the main beam web 3b, positioned parallel to the vertical plate 19 (see Figures 5 and 6). The lower flange-side horizontal plate 23 is further reinforced by sandwiching and fixing it between the reinforcing stiffeners 29 and the vertical plate 19.

[0035] In this example as well, the stress (compressive force) acting on one of the lower flanges 5c of a secondary beam is transmitted to the other lower flange 5c of a secondary beam via the high-strength bolt 17, the connecting plate 25, the horizontal plate 23 on the lower flange side, and the main beam web 3b.

[0036] Furthermore, the configuration of the lower flange joint 11 of the secondary beam described above can also be applied to the upper flange joint 7 of the secondary beam. Such an embodiment is shown in Figures 7 to 9. The secondary beam web joint 9 and the lower flange joint 11 of the main beam-secondary beam joint structure 31 shown in Figures 7 to 9 are the same as those in the examples in Figures 1 to 3, so the same reference numerals are used and their explanations are omitted, and only the upper flange joint 7 of the secondary beam will be described below.

[0037] In this example, as shown in Figure 8, a pair of upper flange-side horizontal plates 33 (shown in dark gray) are joined to both sides of the upper flange 3a of the main beam 3, sandwiching the upper flange 5a of the secondary beam in the width direction. These upper flange-side horizontal plates 33, like the lower flange-side horizontal plates 23, should be welded to the upper flange 3a of the main beam in advance at the factory.

[0038] The width, thickness, and yield strength of the upper flange-side horizontal plate 33 should be set according to the width, thickness, and yield strength of the upper flange 5a of the secondary beam, similar to the lower flange-side horizontal plate 23. The same applies to the clearance provided between the outer edges of the upper flange-side horizontal plate 33 and the upper flange 5a of the secondary beam.

[0039] The sides of the upper flange 5a of the secondary beam are friction-jointed with high-strength bolts to the adjacent upper flange-side horizontal plate 33. Specifically, two joining plates 25 (shown in light gray) are positioned on the upper and lower surfaces, respectively, spanning the upper flange 5a and the upper flange-side horizontal plate 33, and these joining plates 25 are joined to the upper flange 5a and the upper flange-side horizontal plate 33, respectively, with high-strength bolts 17.

[0040] As a result, the stress (tensile force) acting on one of the upper flanges 5a of the secondary beam is transmitted to the other upper flange 5a of the secondary beam via the high-strength bolt 17, the connecting plate 25, the upper flange side horizontal plate 33, and the upper flange 3a of the main beam. To withstand this stress transmission, the diameter and arrangement (number) of the high-strength bolts 17, as well as the specifications of the connecting plate 25 (yield strength, plate thickness, length, etc.), should be designed based on the cross-sectional area and yield strength of the upper flange 5a of the beam.

[0041] Figures 7 to 9 show examples where the beam depth of the main beam 3 and the secondary beam 5 are the same. However, when the beam depth of the secondary beam 5 is smaller than that of the main beam 3, the configuration is as shown in Figures 10 and 11. In the main beam-secondary beam joint structure 35 shown in Figures 10 and 11, the secondary beam upper flange joint 7 has the same configuration as in Figure 8, and the secondary beam lower flange joint 11 has the same configuration as in Figure 5.

[0042] Furthermore, as shown in the main beam-joint structure 37 in Figure 12, the upper flange joint 7 of the secondary beam can be configured as shown in Figure 8, and the lower flange joint 11 of the secondary beam can be configured in a different way. Note that the lower flange joint 11 of the secondary beam in Figure 12 is an example in which the axial end of the lower flange 5c of the secondary beam is butted against the side surface of the lower flange 3c of the main beam and fully penetrated welded.

[0043] In the beam upper flange joint 7 shown in Figures 7, 10, and 12, it is easy to add high-strength bolts 17 according to the stress borne by the beam upper flange 5a, thereby ensuring sufficient joint force for stress transmission.

[0044] As described above, the present invention is characterized by the configuration of the lower beam flange joint 11 described in Figures 2 and 5, and the upper beam flange joint 7 described in Figure 8. The present invention includes any or both of these configurations provided in either the lower beam flange joint 11 and the upper beam flange joint 7. Regarding joints to which the above configuration is not applied, it is sufficient that they are rigidly joined in a way that allows them to exhibit rotational rigidity as a joint, and they may be joined in a way different from those illustrated in Figures 1 to 12.

[0045] For example, in the case of the upper flange joint 7 of the secondary beam, Figure 1 shows an example in which the upper flanges 5a of the secondary beams are joined to each other via the vertical plate 13 and the joining plate 15, but the upper flanges 5a of the secondary beams may also be welded to the upper flange 3a of the main beam. Furthermore, in the case of the beam web joint 9, Figure 1 shows an example in which the beam web 5b and the vertical plate 19 are bolted together via a splice plate 21. However, instead of using the splice plate 21, the vertical plate 19 may be extended towards the beam web 5b and bolted directly to the beam web 5b. Furthermore, in the case of the lower flange joint 11 of the secondary beam, Figure 12 shows an example in which the lower flange 5c of the secondary beam is welded to the lower flange 3c of the main beam. However, a plate-shaped member may be placed across the main beam 3 in the axial direction of the secondary beam, and the lower flange 5c of the secondary beam may be joined to this member by fillet welding. [Explanation of Symbols]

[0046] 1 Large beam / small beam joint structure 3 girder 3a Upper flange of main beam 3b Main beam web 3c Main beam lower flange 5 Small beam 5a Upper flange of secondary beam 5b Small beam web 5c Lower flange of joist 7. Upper flange joint of a secondary beam 9. Beam web joint 11. Lower flange joint of a secondary beam 13 Vertical Plate 15 Joining plate 17 High-strength bolts 19 Vertical Plate 21 Plate 23 Lower flange side horizontal plate 25 Joining plate 27. Main beam / secondary beam joint structure (other embodiment 1) 29 Reinforcement stiffener 31. Main beam / secondary beam joint structure (other embodiment 2) 33 Upper flange side horizontal plate 35. Main beam / secondary beam joint structure (other embodiment 3) 37. Main beam / secondary beam connection structure (other aspects 4)

Claims

1. A main beam made of H-shaped steel is joined to a main beam, with a pair of secondary beams made of H-shaped steel with the same beam depth as the main beam, positioned opposite each other on either side of the main beam in a direction perpendicular to the main beam, wherein A joint section is formed by rigidly connecting the upper flanges of opposing beams to the upper flange of a main beam, or by rigidly connecting the upper flanges of opposing beams to each other via a member, The beam webs of opposing beams are rigidly connected to vertical plates attached to the main beam webs, forming a beam web joint. The lower flanges of opposing joists are joined to the lower flanges of the main beams, and each joists is joined to a pair of horizontal plates on the lower flange side that are positioned to sandwich the lower flanges of the joists in the width direction, and these plates form a joist lower flange joint. The main beam-beam joint structure is characterized in that the lower flange joint of the joist is formed by joining the lower flange of the joist and the horizontal plate on the lower flange side to two joining plates, which are positioned on the upper and lower surfaces of the joist and the horizontal plate on the lower flange side, respectively, with high-strength bolts.

2. A main beam made of H-shaped steel is joined to a main beam, with a pair of secondary beams made of H-shaped steel having a smaller beam depth than the main beam, positioned opposite each other on either side of the main beam in a direction perpendicular to the main beam, A joint section is formed by rigidly connecting the upper flanges of opposing beams to the upper flange of a main beam, or by rigidly connecting the upper flanges of opposing beams to each other via a member, The beam webs of opposing beams are rigidly connected to vertical plates attached to the main beam webs, forming a beam web joint. The lower flanges of opposing joists are joined to the web of the main beam, and each joists is joined to a pair of horizontal plates on the lower flange side that are positioned to sandwich the lower flanges of the joists in the width direction, and the lower flanges of the joists are joined to these joists. The main beam-beam joint structure is characterized in that the lower flange joint of the joist is formed by joining the lower flange of the joist and the horizontal plate on the lower flange side to two joining plates, which are positioned on the upper and lower surfaces of the joist and the horizontal plate on the lower flange side, respectively, with high-strength bolts.

3. The aforementioned beam upper flange joint is formed by joining the upper flanges of opposing beams to a pair of upper flange-side horizontal plates that are arranged to sandwich the beam upper flanges in the width direction and are connected to the upper flange of the main beam. The beam-to-beam joint structure according to claim 1 or 2, characterized in that the beam-to-beam joint is formed by joining the beam-to-beam upper flange to two joining plates, which are positioned on the upper and lower surfaces of the beam-to-beam upper flange and the upper flange-side horizontal plate, respectively, with high-strength bolts.

4. A main beam made of H-shaped steel is joined to a main beam, with a pair of secondary beams made of H-shaped steel positioned opposite each other on either side of the main beam in a direction perpendicular to the main beam, The upper flanges of opposing joists are joined to the upper flange of the main beam, and each is joined to a pair of upper flange-side horizontal plates that are positioned to sandwich the upper flange of the joist in the width direction, forming a joist upper flange joint. The beam webs of opposing beams are rigidly connected to vertical plates attached to the main beam webs, forming a beam web joint. The lower flanges of opposing joists are rigidly connected to the main beam, or the lower flanges of opposing joists are rigidly connected to each other via a member, forming a joist lower flange joint. The main beam-beam joint structure is characterized in that the upper flange joint of the secondary beam is formed by joining the upper flange of the secondary beam and the horizontal plate on the upper flange side to two joining plates, which are positioned on the upper and lower surfaces of the secondary beam upper flange and the horizontal plate on the upper flange side, respectively, with high-strength bolts.

5. The aforementioned bonding plate has a yield strength lower limit of 355 N / mm². 2 The main beam / secondary beam joint structure according to claim 1, 2, or 4, characterized in that it is as described above.

6. The aforementioned bonding plate has a yield strength lower limit of 355 N / mm². 2 The main beam / secondary beam joint structure according to claim 3, characterized in that it is as described above.

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